The world of 3D printing continues to grow. Whereas acrylonitrile butadiene styren (ABS) polylactic acid (PLA) are commonly used 3D filaments, particularly for hobbyists or high-volume manufacturers, new materials enable expanded functionality of 3D printed pieces and parts. Purchasers look for materials that exhibit extended resistance to chemicals, heat or fatigue, and physical properties such as strength, rigidity, flexibility, softness, color and appearance.
Printer makers introduce new 3D printing technologies such as digital light processing (DLP), stereolithography (SLA), selective laser sintering (SLS), fused deposition modelling (FDM) and 3D microfabrication. The ever-expanding list of applications require the adoption of materials such as carbon fibers, polyurethane siloxane copolymers, elastomeric polyurethane (EPU), polyvinyl alcohol (PVA), and polyether ether ketone (PEEK).
Common to most 3D printing methods is the use of polymeric filaments. And common to almost all 3D printing filaments is an extrusion process that creates the spools of printing material. Due to the nature of the 3D printing process, the diameter of the filament requires tight tolerances and control. A strand of filament with a fluctuating diameter creates an inconsistent volume of material and poor layer quality and bonding characteristics.
Single-screw extruders have high pressure build-up and constant output, which is important for maintaining a constant filament diameter. While this process is sufficient for creating simple 3D filaments of ABS or PLA, the single-screw extruders is inefficient at mixing or compounding advanced 3D printing materials that consist of multiple component formulations.
Twin-screw extruders are much better suited to compounding multiple ingredients into a homogeneous blend for creating the filament. However, the twin-screw extrusion process results in a slightly pulsating output, making it difficult to maintain a constant filament diameter.
For the use of these filaments in a 3D printer, however, a constant filament diameter is mandatory as it determines the shape quality and stability of the final printed product. Therefore, a constant output of the extruder is necessary to achieve the desired filament specification. The solution is to add a melt pump to the process to meter material through a set of intermeshing gears. These pumps maintain a consistent pressure and throughput. Melt pumps can increase output, reduce scrap, and control surge.
The Thermo Fisher Scientific Process 11 is a benchtop twin-screw extruder that is ideal for the development and experimentation of new 3D printing materials and printing processes, or for short-run production of advanced 3D filaments. The extruder features minimized material use (20 g), a throughput range of 20g/h to 2.5kg/h, segmented screw design with removable top half barrel for easy clean-up and fast turnaround times. Its geometrically scalable screw and barrel design provides scale-up to larger extruder set-ups.
Our application specialists compared the output of a single-screw extruder, twin-screw extruder, and the addition of a melt pump to a twin-screw extruder to demonstrate the variation and control of 3D filaments using these three processes. Learn more by reading the application note titled, “Use of melt pump to produce filaments for additive manufacturing (3D printing).”
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